Lacplesis (Bearslayer) is the Latvian national hero, a legendary figure like King Arthur, Siegfried, or Roland. He received his name on his eighteenth birthday, when he saved his foster father by killing a bear with his bare hands. He is patriotic, brave, strong, tough, loyal, wise, fair, and virtuous, and loves nature. He fights to preserve Latvia's freedom and its people's way of life against German invaders, who are aided by the Devil. He defeats the Estonian giant, Kalapuisis, in single combat and makes a perilous voyage to the Northern Sea, where he has many adventures on the way back to Latvia.

Once back in Latvia he leads the Latvians in a fight to expel the Germans, and at first they are victorious. Bearslayer now hopes to live in peace with his bride, the beautiful and virtuous Laimdota. Eventually, however, the traitorous warlock, Kangars, discovers Bearslayer's secret (he has bear's ears, and these give him his strength), and reveals this to the German invaders.

By trickery the Black Knight succeeds in cutting off Bearslayer's ears, and the two fight until they fall together into the River Daugava and are never seen again. Without Bearslayer the Latvians are defeated by the Germans, and suffer centuries of occupation by foreign powers. However, Bearslayer is not dead: He sleeps in a golden palace beneath the river, and will one day rise again to bring freedom to his people.